A white LED device, the use of which has recently increased in a general illumination device, a liquid crystal diode (LCD) backlight, vehicle headlights, and the like. The white LED device generally includes a light emitting diode (LED) device emitting blue or near-ultraviolet light and a phosphor converting a light wavelength to visible light by using light emitted from the light emitting device as an excitation source.
In a method for implementing such a white LED according to the related art, as a light emitting device, a blue light emitting diode formed using a InGaN-based material having a wavelength of 450 to 550 nm may be used, and as a phosphor, a YAG-based phosphor emitting yellow light, represented by a compositional formula of (Y,Gd)3(Al,Ga)5O12 may be representatively used. The white LED device allows blue light emitted from a light emitting device to be transmitted through a phosphor layer such that the absorption and scattering thereof are repeated several times within the phosphor layer, and a portion of blue light incident on and absorbed by phosphors in the phosphor layer during this process is mixed with wavelength-converted yellow light, whereby it is perceived as white to the human eye. However, in the case of an oxide-based phosphor such as a silicate or the like, in general, when an excitation source wavelength exceeds 400 nm, since there is a tendency for a decrease in light emission strength, it may not be appropriate for producing relatively highly bright white light by using blue light. In a garnet-based phosphor, represented by YAG, excellent excitation efficiency and light emission efficiency may be provided in blue light, while light emitting efficiency at a relatively high temperature may be reduced.
A nitride-based phosphor, for example, a so-called LSN phosphor having a compositional formula of La3Si6N11, has recently been reported and has excellent characteristics in terms of high temperature characteristics and reliability. However, in the case of an LSN phosphor, there is still a need to develop a phosphor having improved efficiency in order to replace commercialized phosphors of the related art.